save e_incremental exception

Reading a response in the form I tried to use the rescue mode of a signed document in e_incrementale as per the following code: “_pdfdoc.Save (fileName, SDFDoc.SaveOptions.e_incremental)”, but I get an exception that I have attached. However if you use the “_pdfdoc.Save mode (fileName, SDFDoc.SaveOptions.e_remove_unused)” my application works.
I would use the e_incremental mode, but do not understand why I get the exceptiom.
To sign up using your method.

Thank you.

Best regards.

If you are not on PDFNet 6.7.1 then I would recommend trying that first.

Otherwise, can you please re-post the exception message you get.